The new alphabet-series on reversing the second half i.e. last 13 letter:
A
B
C
D
E
F
G
H
I
J
K
L
M
Z
Y
X
W
V
U
T
S
R
Q
P
O
N

The twelfth letter from the right i.e. from N=Y.
So, the fourth letter to the left of Y = K.
Shortcut Method : (4 + 12)th letter from right end
= 16th from right end = K.